Self-aligned middle of the line (mol) contacts

ABSTRACT

Disclosed are methods and integrated circuit (IC) structures. The methods enable formation of a gate contact on a gate above (or close thereto) an active region of a field effect transistor (FET) and provide protection against shorts between the gate contact and metal plugs on source/drain regions and between the gate and source/drain contacts to the metal plugs. A gate with a dielectric cap and dielectric sidewall spacer is formed on a FET channel region. Metal plugs with additional dielectric caps are formed on the FET source/drain regions such that the dielectric sidewall spacer is between the gate and the metal plugs and between the dielectric cap and the additional dielectric caps. The dielectric cap, dielectric sidewall spacer and additional dielectric caps are different materials preselected to be selectively etchable, allowing for misalignment of a contact opening to the gate without risking exposure of any metal plugs and vice versa.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit under 35 U.S.C. §120 as adivisional of presently pending U.S. patent application Ser. No.15/354,212 filed on Nov. 17, 2016, the entire teachings of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the middle of the line (MOL) contactsthat connect semiconductor devices to back end of the line (BEOL) metallevels and, more particularly, to methods of forming integrated circuit(IC) structures with self-aligned MOL contacts to avoid shorts, whileenabling further area scaling, and to the resulting IC structures.

BACKGROUND

Integrated circuit (IC) structures have middle of the line (MOL)contacts that connect the semiconductor devices to back end of the line(BEOL) metal levels. For example, a field effect transistor (FET) canhave a gate contact (also referred to herein as a CB contact) andsource/drain contacts (also referred to herein as CA contacts). The gatecontact can extend vertically through interlayer dielectric (ILD)material from a metal wire or via in the first back end of the line(BEOL) metal level (referred to herein as M0) to the gate of the FET.The source/drain contacts can extend vertically through ILD materialfrom metal wires or vias in the BEOL metal level to metal plugs (alsoreferred to herein as TS contacts), which are on the source/drainregions of the FET. Historically, in order to avoid shorts between thegate contact and the metal plugs, the gate contact is formed on aportion of the gate that is offset from the active region of the FETand, more particularly, on a portion of the gate that extends laterallyover the adjacent isolation region. However, given the ever present needfor size scaling of devices, it would be advantageous to provide amethod that, not only allows for a gate contact to be formed on aportion of the gate directly above the active region (referred to hereinas a CB-over-active or CBoA) or close thereto, but ensures that the riskof a short developing between the gate contact and any of the metalplugs is avoided (or at least significantly reduced).

SUMMARY

In view of the foregoing, disclosed herein are methods of forming anintegrated circuit (IC) structure, which includes one or more fieldeffect transistors (FETs). The disclosed methods allow for a gatecontact to be formed on a portion of a gate aligned above an activeregion of a FET (i.e., a CBoA) or to be formed close thereto (e.g., tobe formed on a portion of a gate in close proximity to the active regionand/or in close proximity to any metal plugs). The disclosed methodsalso provide protection against the development of shorts between thegate contact and any metal plugs on the source/drain regions of the FETand further between the gate and source/drain contacts to the metalplugs. Specifically, in the methods, a gate with a dielectric cap anddielectric sidewall spacer can be formed on the channel region of a FETor, optionally, on the channel regions of multiple FETs. Additionally,metal plugs with additional dielectric caps can be formed on thesource/drain regions of the FET or FETs such that the dielectricsidewall spacer is positioned laterally between the gate and the metalplugs and further between the dielectric cap on the gate and theadditional dielectric caps on the metal plugs. The dielectric cap on thegate, dielectric sidewall spacer and additional dielectric caps on themetal plugs can be made of different dielectric materials preselected tobe selectively etchable, thereby allowing for possible misalignment ofthe contact opening to the gate without risking exposure of any metalplugs and vice versa. Also disclosed are resulting IC structures.

Generally, disclosed herein are methods of forming an integrated circuit(IC) structure, which includes at least one field effect transistor(FET). In the methods, a semiconductor body can be formed and can haveareas designated for source/drain regions and a channel regionpositioned laterally between the source/drain regions. A gate having adielectric cap and a dielectric sidewall spacer can be formed on thechannel region. At least one dielectric layer can be formed so that aportion thereof is above the source/drain regions and positionedlaterally adjacent to the dielectric sidewall spacer. Metal plugopenings can be formed within the at least one dielectric layer so as tobe aligned above the source/drain regions and metal plugs havingadditional dielectric caps can subsequently be formed within the metalplug openings. Thus, the dielectric sidewall spacer will be positionedlaterally between the metal plugs and the gate and further between theadditional dielectric caps and the dielectric cap. The dielectric cap onthe gate, the dielectric sidewall spacer, and the additional dielectriccaps on the metal plugs can be made of different dielectric materials.

An interlayer dielectric material can be deposited above and immediatelyadjacent to the at least one dielectric layer, the dielectric cap on thegate, the dielectric sidewall spacer, and the additional dielectric capson the metal plugs. A first contact opening can be formed through theinterlayer dielectric material and the dielectric cap to the gate.Additionally, second contact openings can be formed through theinterlayer dielectric material and the additional dielectric caps to themetal plugs. The first contact opening and the second contact openingscan be filled with conductive material to form a first contact to thegate and second contacts to the metal plugs, respectively.

Such methods can be used during the formation of a variety of ICstructures such as IC structures that incorporate planar FET(s) ornon-planar FET(s), IC structures that incorporate a conventionalgate-first gate or a replacement metal gate, IC structures thatincorporate a FET with multiple semiconductor bodies, IC structures thatincorporate a complementary metal oxide semiconductor (CMOS) device withboth an N-type FET (NFET) and a P-type FET (PFET), IC structures thatincorporate a CMOS devices where the NFET and PFET have a shared gate,etc.

Thus, for example, one method embodiment disclosed herein can be used toform an IC structure that incorporates multiple non-planar FETs and,particularly, that incorporates a CMOS device, where the NFET and PFETare non-planar FETs each with one or more semiconductor bodies and wherethe NFET and PFET share a replacement metal gate.

Specifically, this method embodiment can include forming at least onefirst semiconductor body for a first-type field effect transistor (e.g.,an NFET) and at least one second semiconductor body for a second-typefield effect transistor (e.g., a PFET). Each first semiconductor bodyhas areas designated for first source/drain regions and a first channelregion positioned laterally between the first source/drain regions andeach second semiconductor body can have areas designated for secondsource/drain regions and a second channel region positioned laterallybetween the second source/drain regions.

A sacrificial gate having a dielectric sidewall spacer can be formedacross the first channel region(s) in the first semiconductor body(ies)and further across the second channel region(s) in the secondsemiconductor body(ies). Additionally, epitaxial semiconductor materialcan be deposited on the first source/drain regions to form raised firstsource/drain regions and on the second source/drain regions to formraised second source/drain regions.

A conformal dielectric layer can be formed over the sacrificial gate,the raised first source/drain regions and the raised second source/drainregions. Then, an additional dielectric layer can be formed on theconformal dielectric layer.

The sacrificial gate can subsequently be removed and replaced with areplacement metal gate having a dielectric cap. Metal plug openings canthen be formed through the additional dielectric layer and the conformaldielectric layer to the raised first source/drain regions and the raisedsecond source/drain regions and metal plugs having additional dielectriccaps can be formed in the metal plug openings. The metal plugs can beformed such that the dielectric sidewall spacer and conformal dielectriclayer are positioned laterally between the metal plugs and the gate andfurther between the additional dielectric caps and the dielectric cap.The dielectric cap, the dielectric sidewall spacer, and the additionaldielectric caps can be made of different dielectric materials.Furthermore, the dielectric sidewall spacer and the conformal dielectriclayer can be made of the same dielectric material.

An interlayer dielectric material can be deposited over the dielectriccap, the dielectric sidewall spacer, the conformal dielectric layer andthe additional dielectric caps. A first contact opening can be formedthrough the interlayer dielectric material and the dielectric cap to thereplacement metal gate. Additionally, second contact openings can beformed through the interlayer dielectric material and the additionaldielectric caps to the metal plugs. The first contact opening and thesecond contact openings can be filled with conductive material to form afirst contact to the replacement metal gate and second contacts to themetal plugs, respectively.

In each of methods described above the different dielectric materialsused for the dielectric cap on the replacement metal gate, thedielectric sidewall spacer on the replacement metal gate and theadditional dielectric caps on the metal plugs can be preselected so thatthe dielectric cap is selectively etchable over the dielectric sidewallspacer and the additional dielectric caps during the forming of thefirst contact opening. Thus, the first contact will be self-aligned tothe gate (i.e., will be a self-aligned first contact), regardless ofwhether any misalignment occurs, and the risk of a short occurringbetween the first contact and any of the metal plugs is avoided (or atleast significantly reduced). The different dielectric materials canfurther be preselected so that the additional dielectric caps areselectively etchable over the dielectric sidewall spacer and thedielectric cap during the forming of the second contact openings. Thus,the second contacts will be self-aligned to the metal plugs (i.e., willbe self-aligned second contacts), regardless of whether any misalignmentoccurs, and the risk of a short occurring between any of the secondcontacts and the gate is avoided (or at least significantly reduced).

Also disclosed herein are integrated circuit (IC) structures, whichinclude at least one field effect transistor (FET). The FET can includea semiconductor body with source/drain regions and a channel regionpositioned laterally between the source/drain regions. A gate having adielectric cap and a dielectric sidewall spacer can be on the channelregion. At least one dielectric layer can be above the source/drainregions and positioned laterally adjacent to the dielectric sidewallspacer. Additionally, metal plugs having additional dielectric caps,respectively, can be within metal plug openings in the at least onedielectric layer aligned above the source/drain regions such that thedielectric sidewall spacer is positioned laterally between the metalplugs and the gate and further between the additional dielectric capsand the dielectric cap. The dielectric cap, the dielectric sidewallspacer, and the additional dielectric caps can be made of differentdielectric materials.

An interlayer dielectric material can be above and immediately adjacentto the at least one dielectric layer, the dielectric cap, the dielectricsidewall spacer, and the additional dielectric caps. A first contactopening can extend vertically through the interlayer dielectric materialand the dielectric cap to the gate. Additionally, second contactopenings can extend vertically through the interlayer dielectricmaterial and the additional dielectric caps to the metal plugs. Thefirst contact opening and the second contact openings can be filled withconductive material to form a first contact to the gate and secondcontacts to the metal plugs, respectively.

The above described IC structures can, for example, incorporate planarFET(s) or non-planar FET(s), can incorporate a conventional gate-firstgate or a replacement metal gate, can incorporate a FET with multiplesemiconductor bodies, can incorporate a complementary metal oxidesemiconductor (CMOS) device with both an N-type FET (NFET) and a P-typeFET (PFET), can incorporate a CMOS devices where the NFET and PFET havea shared gate, etc.

In any case, in each of these IC structures the different dielectricmaterials used for the dielectric cap on the gate, the dielectricsidewall spacer on the gate and the additional dielectric caps on themetal plugs are preselected so that the dielectric cap is selectivelyetchable over the dielectric sidewall spacer and the additionaldielectric caps during the forming of the first contact opening. Thus,the first contact is self-aligned to the gate (i.e., is a self-alignedfirst contact), regardless of any misalignment, and the risk of a shortoccurring between the first contact and any of the metal plugs isavoided (or at least significantly reduced). The different dielectricmaterials can further be preselected so that the additional dielectriccaps are selectively etchable over the dielectric sidewall spacer andthe dielectric cap during the forming of the second contact openings.Thus, the second contacts are self-aligned to the metal plugs (i.e., areself-aligned second contacts), regardless of any misalignment, and therisk of a short occurring between any of the second contacts and thegate is avoided (or at least significantly reduced).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be better understood from the followingdetailed description with reference to the drawings, which are notnecessarily drawn to scale and in which:

FIG. 1 is a flow diagram illustrating methods of forming an integratedcircuit (IC) structure that incorporates at least one field effecttransistor (FET), where the FET has a gate and where a gate contact tothe gate lands on a portion of the gate above (or close thereto) anactive region;

FIGS. 2A-2B are top view and cross section X-X′ diagrams illustrating apartially completed structure formed according to the methods of FIG. 1;

FIGS. 3A-3B are top view and cross section X-X′ diagrams illustrating apartially completed structure formed according to the methods of FIG. 1;

FIGS. 4A-4B are top view and cross section Y-Y′ diagrams illustrating apartially completed structure formed according to the methods of FIG. 1;

FIGS. 5A-5D are top view, cross section X-X′, cross section Y-Y′ andcross section Z-Z′ diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIGS. 6A-6D are top view, cross section X-X′, cross section Y-Y′ andcross section Z-Z′ diagrams illustrating a partially completed structureformed according to the methods of FIG. 1;

FIGS. 7A-7B are top view and cross section X-X′ diagrams illustrating apartially completed structure formed according to the methods of FIG. 1;

FIG. 8 is a cross section X-X′ diagram illustrating a partiallycompleted structure formed according to the methods of FIG. 1;

FIGS. 9A-9C are top view, cross section Y-Y′ and cross section Z-Z′diagrams illustrating a partially completed structure formed accordingto the methods of FIG. 1;

FIGS. 10A-10B are top view and cross section Y-Y′ diagrams illustratinga partially completed structure formed according to the methods of FIG.1;

FIGS. 11A-11C are top view, cross section X-X′ and cross section W-W′diagrams illustrating a partially completed structure formed accordingto the methods of FIG. 1;

FIG. 12 is a cross section W-W′ diagram illustrating a portion of acompleted structure formed according to the methods of FIG. 1;

FIGS. 13A-13B are top view and cross section W-W′ diagrams illustratinga partially completed structure formed according to the methods of FIG.1;

FIG. 14 is a cross section W-W′ diagram illustrating a portion of acompleted structure formed according to the methods of FIG. 1;

FIGS. 15A-15C are top view, cross section Y-Y′ and cross section Z-Z′diagrams illustrating a partially completed structure formed accordingto the methods of FIG. 1;

FIG. 16 is a cross section Z-Z′ diagram illustrating a portion of acompleted structure formed according to the methods of FIG. 1;

FIGS. 17A-17B are top view and cross section Z-Z′ diagrams illustratinga partially completed structure formed according to the methods of FIG.1;

FIG. 18 is a cross section Z-Z′ diagram illustrating a portion of acompleted structure formed according to the methods of FIG. 1; and,

FIG. 19A-19C are cross section X-X′, cross section W-W′ and crosssection Z-Z′ diagrams illustrating different portions of an integratedcircuit (IC) structure that incorporates at least one field effecttransistor (FET), where the FET has a gate and where a gate contact tothe gate lands on a portion of the gate above (or close thereto) anactive region.

DETAILED DESCRIPTION

As mentioned above, integrated circuit (IC) structures have middle ofthe line (MOL) contacts that connect the semiconductor devices to backend of the line (BEOL) metal levels. For example, a field effecttransistor (FET) can have a gate contact (also referred to herein as aCB contact) and source/drain contacts (also referred to herein as CAcontacts). The gate contact can extend vertically through interlayerdielectric (ILD) material from a metal wire or via in the first back endof the line (BEOL) metal level (referred to herein as M₀) to the gate ofthe FET. The source/drain contacts of the FET can extend verticallythrough ILD material from metal wires or vias in the BEOL metal level tometal plugs (also referred to herein as TS contacts), which are on thesource/drain regions of the FET. Historically, in order to avoid shortsbetween the gate contact and the metal plugs, the gate contact is formedon a portion of the gate that is offset from the active region of theFET and, more particularly, on a portion of the gate that extendslaterally over the adjacent isolation region. However, given the everpresent need for size scaling of devices, it would be advantageous toprovide a method that, not only allows for a gate contact to be formedon a portion of the gate directly above the active region (referred toherein as a CB-over-active or CBoA) or close thereto, but ensures thatthe risk of a short developing between the gate contact and any of themetal plugs is avoided (or at least significantly reduced).

In view of the foregoing, disclosed herein are methods of forming anintegrated circuit (IC) structure, which includes one or more fieldeffect transistors (FETs). The disclosed methods allow for a gatecontact to be formed on a portion of a gate aligned above an activeregion of a FET (i.e., a CBoA) or to be formed close thereto (e.g., tobe formed on a portion of a gate in close proximity to the active regionand/or in close proximity to any metal plugs). The disclosed methodsalso provide protection against the development of shorts between thegate contact and any metal plugs on the source/drain regions of the FETand further between the gate and source/drain contacts to the metalplugs. Specifically, in the methods, a gate with a dielectric cap anddielectric sidewall spacer can be formed on the channel region of a FETor, optionally, on the channel regions of multiple FETs. Additionally,metal plugs with additional dielectric caps can be formed on thesource/drain regions of the FET or FETs such that the dielectricsidewall spacer is positioned laterally between the gate and the metalplugs and further between the dielectric cap on the gate and theadditional dielectric caps on the metal plugs. The dielectric cap,dielectric sidewall spacer and additional dielectric caps can be made ofdifferent dielectric materials preselected to be selectively etchable,thereby allowing for possible misalignment of the contact opening to thegate without risking exposure of any metal plugs and vice versa. Alsodisclosed are resulting IC structures.

Generally, disclosed are methods of forming an integrated circuit (IC)structure that incorporates at least one field effect transistor (FET),where the FET has a gate and where a gate contact to the gate lands on aportion of the gate above (or close thereto) an active region (i.e.,where a gate contact is a CBoA). Referring to the flow diagram of FIG.1, in these methods, a semiconductor wafer is provided (101) and one ormore semiconductor bodies can be formed on the wafer (102). Eachsemiconductor body can be a planar semiconductor body for a planar FETor a non-planar semiconductor body (e.g., a semiconductor fin) for anon-planar FET, such as a fin-type FET (finFET) or a trigate FET. In anycase, each semiconductor body can have areas designated for a channelregion and for source/drain regions of the FET, wherein the channelregion is positioned laterally between the source/drain regions.

A gate, which has a dielectric cap and a dielectric sidewall spacer, canbe formed across the channel region of the semiconductor body (or,across the channel regions of multiple semiconductor bodies, ifapplicable) (104). This gate can be a conventional gate-first gate(e.g., a gate with a silicon dioxide gate dielectric layer and apolysilicon gate conductor layer or any other suitable gate-first gateconfiguration. Alternatively, this gate can be a replacement metal gate(e.g., a gate with a high-K gate dielectric layer and metal gateconductor layer or any other suitable replacement metal gateconfiguration) formed by removing a previously formed sacrificial gateand replacing that sacrificial gate with a metal gate (as discussed ingreater detail below). In any case, those skilled in the art willrecognize that the gate will be positioned adjacent to the top surfaceof the semiconductor body at the channel region in the case of a planarFET and adjacent to opposing sidewalls and, optionally, above the topsurface of the semiconductor body in the case of a non-planar FET.

Additionally, at least one dielectric layer (e.g., a conformaldielectric layer and an additional dielectric layer, as discussed ingreater detail below) can be deposited such that the dielectric layer(s)are stacked above the semiconductor body(ies) at the source/drainregions and further positioned laterally adjacent to the dielectricsidewall spacer (105). Subsequently, metal plug openings can be formedin the dielectric layer(s) so as to be aligned above the source/drainregions and metal plugs having additional dielectric caps, respectively,can be formed within the metal plug openings such that the dielectricsidewall spacer is positioned laterally between the metal plugs and thegate and further between the additional dielectric caps and thedielectric cap (106).

At processes 104-106, the dielectric cap, the dielectric sidewallspacer, and the additional dielectric caps should all be made ofdifferent dielectric materials. These different materials can bepreselected so that, during subsequent processing (e.g., see processsteps 110-114, discussed in greater detail below), the dielectric cap isselectively etchable over the dielectric sidewall spacer and theadditional dielectric caps and so that the additional dielectric capsare selectively etchable over the dielectric sidewall spacer and thedielectric cap. Exemplary dielectric materials can include, for example,silicon nitride for the dielectric cap, silicon carbon oxide for thedielectric sidewall spacer and silicon oxide for the additionaldielectric caps. Alternatively, any other suitable dielectric materialscould be used. A chemical mechanical polishing (CMP) process can then beperformed. As a result of this CMP process, the dielectric cap anddielectric sidewall spacer on the gate and the additional dielectriccaps on the metal plugs all have approximately co-planar top surfaces.Those skilled in the art will recognize that, while ideally the topsurfaces of the dielectric cap, dielectric sidewall spacer andadditional dielectric caps will be perfectly co-planar following CMP,variations in the reactions of the different dielectric materials to thechemical and/or mechanical forces imparted thereon may result in thelevels of the top surfaces of these features being slightly varied.

Subsequently, an interlayer dielectric (ILD) material can be depositedsuch that it covers and, more particularly, such that it is above andimmediately adjacent to the top surfaces of the at least one dielectriclayer, the dielectric cap, the dielectric sidewall spacer, and theadditional dielectric caps (108). After the ILD material is deposited,another CMP process can be performed.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can be formed (110). The MOLcontacts can include at least one first contact to the gate (referred toherein as a gate contact). The first contact can be formed so as to bealigned above the active region of the FET being formed or close thereto(e.g., aligned above a portion of the gate in close proximity to theactive region or aligned above a portion of the gate in close proximityto any metal plugs). The MOL contacts can also include second contacts(referred to herein as source/drain contacts) to the metal plugs, which,as mentioned above, are above the source/drain regions. It should benoted that formation a first contact opening for the first contact andsecond contact openings for the second contacts at process 110 should beperformed using separate etch processes. Specifically, the first contactopening for the first contact can be formed through the ILD material andthe dielectric cap to the gate using an etch process that is selectiveto the material of the dielectric cap over the materials of thedielectric sidewall spacer and the additional dielectric caps (112).Additionally, the second contact openings for the second contacts can beformed through the ILD material and the additional dielectric caps tothe metal plugs using a different etch process that is selective to thematerial of the additional dielectric caps over the materials of thedielectric cap and the dielectric sidewall spacer (114). The firstcontact opening and the second contact openings can be filled withconductive material using the same or different deposition processes,thereby forming the first contact to the gate and the second contacts tothe metal plugs.

Since the dielectric cap on the gate is selectively etchable over thedielectric sidewall spacer and the additional dielectric caps duringformation of the first contact opening, the first contact will beself-aligned to the gate (i.e., will be a self-aligned first contact),regardless of whether any misalignment occurs, and the risk of a shortoccurring between the first contact and any of the metal plugs isavoided (or at least significantly reduced). Similarly, since theadditional dielectric caps are selectively etchable over the dielectricsidewall spacer and the dielectric cap during formation of the secondcontact openings, the second contacts will be self-aligned to the metalplugs (i.e., will be self-aligned second contacts), regardless ofwhether any misalignment occurs, and the risk of a short occurringbetween any of the second contacts and the gate is avoided (or at leastsignificantly reduced).

The above-described methods can be used during the formation of avariety of different IC structures including, but not limited to, ICstructures that incorporate planar FET(s) or non-planar FET(s), ICstructures that incorporate a conventional gate-first gate or areplacement metal gate, IC structures that incorporate a complementarymetal oxide semiconductor (CMOS) device with both and N-type FET (NFET)and P-type FET (PFET), IC structures that incorporate a CMOS devicewhere the NFET and PFET share a gate, etc.

For purposes of illustration, the method steps are described in evengreater detail below and illustrated in the drawings with reference tothe formation of an IC structure that incorporates multiple non-planarFETs (e.g., finFETs) and, particularly, that incorporates a CMOS devicewith both a non-planar NFET with multiple semiconductor bodies and anon-planar PFET with multiple semiconductor bodies, where the NFET andPFET share a replacement metal gate.

Referring again to the flow diagram of FIG. 1, in this method embodimenta semiconductor wafer can be provided and forming multiple semiconductorbodies on that semiconductor wafer (101-102, See FIGS. 2A-2B).

The semiconductor wafer provided at process 101 can be, for example, asemiconductor-on-insulator (SOI) wafer, as shown in FIG. 2B, thatincludes a semiconductor substrate 202 (e.g., a silicon substrate), aninsulator layer 203 (e.g., a buried oxide (BOX) layer or other suitableinsulator layer on the semiconductor substrate) and a semiconductorlayer (e.g., a silicon layer or other suitable semiconductor layer) onthe insulator layer 203. Alternatively, a bulk semiconductor wafer(e.g., a bulk silicon wafer or other suitable bulk semiconductor wafer)could be used.

At process 102, one or more first semiconductor bodies 210 for afirst-type field effect transistor (e.g., an NFET) and one or moresecond semiconductor bodies 220 for a second-type field effecttransistor (e.g., a PFET) can be formed, wherein each firstsemiconductor body 210 has areas designated for first source/drainregions 212 and a first channel region 211 positioned laterally betweenthe first source/drain regions 212 and wherein each second semiconductorbody 220 has areas designated for second source/drain regions 222 and asecond channel region 221 positioned laterally between the secondsource/drain regions 222. As illustrated, these semiconductor bodies210, 220 can be fin-shaped semiconductor bodies (i.e., relatively thinrectangular semiconductor bodies). Such fin-shaped semiconductor bodiescan be patterned and etched from the semiconductor layer of the SOIwafer (or, alternatively, from the upper portion of a bulk semiconductorsubstrate, when isolation from the lower portion of the bulksemiconductor substrate is provided by buried well regions). Techniquesfor forming such fin-shaped semiconductor bodies (e.g., lithographicpatterning techniques or sidewall image transfer techniques) are wellknown in the art and, thus, the details have been omitted from thisspecification in order to allow the reader to focus on the salientaspects of the disclosed method. It should be noted that the firstchannel regions 211 and the second channel regions 221 can beappropriately doped, either before or after formation of thesemiconductor bodies, so that first channel regions 211 of thefirst-type FET (e.g., the NFET) have, for example, a second-typeconductivity at a relatively low conductivity level (e.g., a P−conductivity) and so that the second channel regions 221 of thesecond-type FET (e.g., the PFET) have, for example, a first-typeconductivity at a relatively low conductivity level (e.g., an N−conductivity).

A replacement metal gate, which has a dielectric cap and a dielectricsidewall spacer, can be formed across the first channel regions 211 ofthe first semiconductor bodies 210 and further across the second channelregions 221 of the second semiconductor bodies 220 (104).

Specifically, to form the replacement metal gate with the dielectric capand dielectric sidewall spacer at process 104, a first sacrificial layercan be formed over the semiconductor bodies 210, 220 and a secondsacrificial layer, which is different from the first sacrificial layer,can be formed on the first sacrificial layer. The first and secondsacrificial layers can be patterned and etched to form a sacrificialgate 231 with a sacrificial cap 232, wherein the sacrificial gate 231 isadjacent to the first channel regions 211 and the second channel regions221. For example, the sacrificial gate 231 can be immediately adjacentto the opposing sidewalls of the semiconductor bodies 210, 220 at thechannel regions 211, 221 and, optionally, can be above the top surfacesof the semiconductor bodies 210, 220 at the channel regions 211, 221such that the sacrificial gate 231 traverses the semiconductor bodies210, 220 (see FIGS. 2A-2B).

Next, a dielectric sidewall spacer 241 can be formed on the sidewalls ofthe sacrificial gate 231 (see FIGS. 3A-3B). That is, a relatively thinconformal dielectric layer can be deposited over the sacrificial gate231 with its sacrificial cap 232 and further over the source/drainregions 212, 222 of the semiconductor bodies 210, 220 that extendlaterally beyond the sacrificial gate 231. Then, a directional etchprocess can be performed so as to remove the conformal dielectric layerfrom horizontal surfaces and from the sidewalls of the source/drainregions 212, 222 of the semiconductor bodies 210, 220. Those skilled inthe art will recognize that the height of the sacrificial cap 232 shouldbe equal to or greater than the height of the semiconductor bodies 210,220 so that the conformal dielectric layer can be removed from thesidewalls of the source/drain regions 212, 222 without exposing thesidewalls of the sacrificial gate 231.

Optionally, epitaxial semiconductor material (e.g., epitaxial silicon orany other suitable epitaxial semiconductor material) can be deposited onexposed portions of the first semiconductor bodies (i.e., on the firstsource/drain regions 212) to form raised first source/drain regions 213for the first-type field effect transistor on opposing sides of thesacrificial gate 231 and further on exposed portions of the secondsemiconductor bodies (i.e., on the second source/drain regions 222) toform raised second source/drain regions 223 for the second-type fieldeffect transistor on the opposing sides of the sacrificial gate 231 (seeFIGS. 4A-4B). Optionally, the epitaxial semiconductor material onadjacent first source/drain regions 212 can be merged into a singleregion and, similarly, the epitaxial semiconductor material on adjacentsecond source/drain regions 222 can be merged into a single region, asillustrated).

Optionally, masked dopant implantation processes can subsequently beperformed to dope the first source/drain regions 212 (or, if applicable,the raised first source/drain regions 213) with a first dopant so as tohave a first-type conductivity at a relatively high conductivity level(e.g., N+ conductivity) and to further dope the second source/drainregions 222 (or, if applicable, the raised second source/drain regions223) with a second dopant so as to have a second-type conductivity at arelatively high conductivity level (e.g., P+ conductivity).

Following the masked dopant implantation processes, another conformaldielectric layer 242 can be deposited over the partially completedstructure (see FIGS. 5A-5D). It should be noted that this conformaldielectric layer 242 could be made of the same dielectric material asthat used to make the dielectric sidewall spacer 241 on the sacrificialgate 231.

After the conformal dielectric layer 242 is deposited, an additionaldielectric layer 250 can be formed on the conformal dielectric layer 242and then planarized (see FIGS. 6A-6D). Specifically, a blanketadditional dielectric layer 250 can be deposited over the conformaldielectric layer 242 and then a chemical mechanical polishing (CMP)process can be performed in order to expose the top surface of thesacrificial gate 231. Optionally, before a CMP process is performed toexpose the sacrificial gate 231, a CMP process can be performed toexpose the sacrificial cap 232 and the additional dielectric layer 250can be recessed. In this case, the removed dielectric material can bereplaced with a material that is generally the same but with a differentdensity (e.g., a greater density), which is more suitable for use withthe CMP process that exposes the sacrificial gate 231.

In any case, once the top surface of the sacrificial gate 231 isexposed, it can be selectively removed (e.g., using an etch process thatselectively etches the sacrificial material of the sacrificial gate 231over the dielectric materials of the dielectric sidewall spacer 241,conformal dielectric layer 242 and additional dielectric layer 250.After the sacrificial gate 231 is selectively removed, it can bereplaced with a replacement metal gate 260 (see FIGS. 7A-7B). Forexample, after the sacrificial gate 231 is selectively removed, aconformal high-K gate dielectric layer 261 can be deposited so as toline the gate opening created by the removal of the sacrificial gate andone or more metal layers 262-263 can be deposited onto the gatedielectric layer 261. Although not shown, optionally, different gatedielectric layers and/or different metal layers can be used for a firstportion of the replacement metal gate 260 over the first channel regions211 as compared to a second portion of the replacement metal gate 260over the second channel regions 221 (e.g., to achieve different workfunctions in the different portions of the gate). In any case, achemical mechanical polishing (CMP) process can be performed to removeall gate materials from above the top surface of the additionaldielectric layer 250.

Once the replacement metal gate 260 is formed, it can be recessed and afirst dielectric cap layer can be deposited and a CMP process can beperformed, thereby forming a dielectric cap 252 on the replacement metalgate 260 (see FIG. 8). Thus, as illustrated, the replacement metal gate260 formed at process 104 has both a dielectric cap 252 and a dielectricsidewall spacer 241.

Next, metal plugs having additional dielectric caps, respectively, canbe formed on and, particularly, above the raised first source/drainregions 213 of the NFET and the raised second source/drain regions 223of the PFET such that the dielectric sidewall spacer 241 and a verticalsection of the conformal dielectric layer 242 are positioned laterallybetween the metal plugs and the gate 260 and further between theadditional dielectric caps and the dielectric cap 252 (106).

Specifically, to form the metal plugs having additional dielectric capsat process 106, metal plug openings 255 can be formed (e.g.,lithographically patterned and etched) through the additional dielectriclayer 250 and the conformal dielectric layer 242 to the raised firstsource/drain regions 213 and the raised second source/drain regions 223(see FIGS. 9A-9C). Then, the metal plugs 256 (e.g., tungsten or cobaltplugs) having the additional dielectric caps 257 can be formed in themetal plug openings 255 (see FIGS. 10A-10B). That is, a metal layer(e.g., a tungsten or cobalt layer) can be deposited into the metal plugopenings 255 and recessed, thereby forming the metal plugs 256. Afterthe metal layer is recessed, a second dielectric cap layer can bedeposited and a CMP process can be performed, thereby forming additionaldielectric caps 257 on the metal plugs 256 and ensuring that thedielectric cap 252 (which is formed above and immediately adjacent tothe top surface of the replacement metal gate 260), the dielectricsidewall spacer 241 (which is formed immediately adjacent to thesidewalls of the sacrificial gate and which remains in place on thesidewalls of the replacement metal gate 260), the vertical section ofthe conformal dielectric layer 242 (which is positioned laterallyadjacent to the dielectric sidewall spacer 241), the additionaldielectric caps 257 (which are formed above and immediately adjacent tothe metal plugs 256) and the additional dielectric layer 250 all haveapproximately co-planar top surfaces. Those skilled in the art willrecognize that, while ideally the top surfaces of the dielectric cap,dielectric sidewall spacer and additional dielectric caps will beperfectly co-planar following CMP, variations in the reactions of thedifferent dielectric materials to the chemical and/or mechanical forcesimparted thereon may result in the levels of the top surfaces of thesefeatures being slightly varied.

It should be noted that, at processes 104-106, the dielectric cap 252,the dielectric sidewall spacer 241, and the additional dielectric caps257 should all made of different dielectric materials. Additionally, theconformal dielectric layer 242 can be made of the same dielectricmaterial as the dielectric sidewall spacer 241 and the additionaldielectric layer 250 can be made of the same dielectric material as theadditional dielectric caps 257. The various dielectric materials can bepreselected so that, during subsequent processing (e.g., see processsteps 110-114, discussed in greater detail below), the dielectric cap252 is selectively etchable over the dielectric sidewall spacer 241, theconformal dielectric layer 242 and the additional dielectric caps 257and so that the additional dielectric caps 257 are selectively etchableover the dielectric sidewall spacer 241, the conformal dielectric layer242 and the dielectric cap 252. Exemplary dielectric materials caninclude, for example, silicon nitride for the dielectric cap 252,silicon carbon oxide for the dielectric sidewall spacer 241 and theconformal dielectric layer 242 and silicon oxide for the additionaldielectric caps 25 and the additional dielectric layer 250.Alternatively, any other suitable dielectric materials could be used.

Subsequently, an interlayer dielectric (ILD) material 280 can bedeposited such that it covers the dielectric cap 252, dielectricsidewall spacer 241, the vertical section of the conformal dielectriclayer 242 (which is positioned laterally adjacent to the dielectricsidewall spacer 241), and additional dielectric caps 257 (108). The ILDmaterial can be, for example, silicon oxide or any other suitable ILDmaterial (e.g., borophosphosilicate glass (BPSG), tetraethylorthosilicate (TEOS), fluorinated tetraethyl orthosilicate (FTEOS),etc.). After the ILD material is deposited, another CMP process can beperformed.

To complete the IC structure, both middle of the line (MOL) contacts andback end of the line (BEOL) metal levels can be formed (110). The MOLcontacts can include at least one first contact to the replacement metalgate 260 (referred to herein as a gate contact). The first contact can,for example, be formed so as to be aligned above the active region ofthe FETs being formed (as illustrated) or close thereto (e.g., alignedabove a portion of the gate in close proximity to the active region oraligned above a portion of the gate in close proximity to any metalplugs). The MOL contacts can also include second contacts (referred toherein as source/drain contacts) to the metal plugs 256. It should benoted that formation of a first contact openings for the first contactand second contact openings for the second contacts at process 110should be performed using separate etch processes.

For example, a first contact opening 281 for a first contact to thereplacement metal gate 260 can be formed through the ILD material 280and the dielectric cap 252 to the replacement metal gate 260 using anetch process that is selective to the material of the dielectric cap 252(e.g., selective to silicon nitride) over the materials of thedielectric sidewall spacer 241 and conformal dielectric layer 242 andthe additional dielectric caps 257 (e.g., over silicon carbon oxide andsilicon oxide) (112, see FIGS. 11A-11C). For purposes of illustration,only a single first contact opening 281 is shown. However, it should beunderstood that any number of one or more first contact openings couldbe formed to the replacement metal gate 260. In any case, the firstcontact opening 281 can be filled with conductive material (e.g.,tungsten, cobalt, copper, or any other suitable conductive material),thereby forming a first contact 285 (see FIG. 12). Since the dielectriccap 252 on the replacement metal gate 260 is selectively etchable overthe dielectric sidewall spacer 241, the conformal dielectric layer 242and the additional dielectric caps 257, the first contact 285 will beself-aligned to the replacement metal gate 260 (i.e., will be aself-aligned first contact), regardless of whether any misalignmentoccurs, and the risk of exposure of any of the metal plugs 256 thatcould result in shorting between the first contact 285 and the metalplugs 256 is avoided (or at least significantly reduced). For example,referring to the misaligned first contact opening 281′ shown in FIGS.13A-13B, when the first contact opening 281′ is offset from thereplacement metal gate 260 (e.g., due to overlay control issues) suchthat it has a first portion that overlaps the replacement metal gate 260and a second portion that overlaps a metal plug 256, etching of thesecond portion will stop on the additional dielectric cap 257, on thevertical section of the conformal dielectric layer 242 and on thedielectric sidewall spacer 241 and etching of the first portion willcontinue through the dielectric cap 252 stopping on the replacementmetal gate 260. Thus, the first portion of the misaligned first contactopening 281′ will be deeper than the second portion and the methodthereby provides protection against the development of a short betweenthe misaligned first contact 285′ and the metal plug 256 upon filling ofthe misaligned first contact opening 281′ with conductive material (asshown in FIG. 14).

Additionally, second contact openings 282 for the second contacts to themetal plugs 256 can be formed through the ILD material 280 and theadditional dielectric caps 257 to the metal plugs 256 using a differentetch process that is selective to the material of the additionaldielectric caps 257 (e.g., silicon oxide) over the materials of thedielectric cap 252 (e.g., silicon nitride) and the dielectric sidewallspacer 241 and conformal dielectric layer 242 (114, see FIGS. 15A-15C).The second contact openings 282 can be filled with conductive material(e.g., tungsten, cobalt, copper, or any other suitable conductivematerial), thereby forming second contacts 286 (see FIG. 16). Since theadditional dielectric caps 257 on the metal plugs 256 are selectivelyetchable over the dielectric sidewall spacer 241, the conformaldielectric layer 242 and the dielectric cap 252, the second contacts 286will be self-aligned to the metal plugs 256 (i.e., will be self-alignedsecond contacts), regardless of any misalignment that occurs, and therisk of exposure of any of the replacement metal gate 260 that couldresult in shorting between a second contact 286 and the replacementmetal gate 260 is avoided (or at least significantly reduced). Forexample, referring to the misaligned second contact openings 282′ shownin FIGS. 17A-17B, when any of the second contact openings are offsetfrom the metal plugs 256 (e.g., due to overlay control issues) so as tohave a first portion that overlaps a metal plug 256 and a second portionthat overlaps the replacement metal gate 260, etching of the secondportion will stop on the dielectric cap 252, on the dielectric sidewallspacer 241 and on the vertical section of the conformal dielectric layer242 and etching of the first portion will continue through theadditional dielectric cap 257 stopping on the metal plug 256. Thus, thefirst portion of the misaligned second contact opening 282′ will bedeeper than the second portion and the method thereby protects againstthe development of a short between any misaligned second contact 286′and the replacement metal gate 260 upon filling of the misaligned secondcontact opening 282′ with conductive material (as shown in FIG. 18).

As mentioned above, the metal plugs 256 are formed within metal plugopenings 255 that extend vertically through the additional dielectriclayer 250 to the raised first source/drain regions 213 and the raisedsecond source/drain regions 223. Also, as mentioned above, theadditional dielectric layer 250 and the additional dielectric caps 257on the metal plugs 256 can be made of the same dielectric material(e.g., silicon oxide). Thus, at process 114 (FIG. 1), any portion of theadditional dielectric layer 250 that is adjacent to a metal plug 256 andthat is exposed during the forming of a misaligned second contactopenings 282′ will be etched away leaving a divot 289, as shown in FIG.17B. Such a divot 289 at least partially exposes a sidewall of the metalplug 256. In this case, the divot 289 will be filled with the conductivematerial during the filling of the misaligned second contact openings282′, thereby increasing interface area between the misaligned secondcontact 286′ and the metal plug 256, reducing contact resistance andimproving performance.

While separate processes must be used to form (i.e., lithographicallypattern and etch) the first contact opening for the first contact andthe second contact openings for the second contacts, the same ordifferent deposition processes can be used to fill these openings withconductive material. Thus, the same or different conductive materialscan fill the first contact opening and the second contact openings.Additionally, a first single damascene process and a second singledamascene process can be used to form the first contact and the secondcontacts, respectively, and, after these two single damascene processesare performed, the BEOL metal levels can be formed. Alternatively, onesingle damascene process can be used to form either the first contact orthe second contacts and, after this single damascene process isperformed, a dual damascene process can be used to form the remainingMOL contacts and the first metal level (referred to herein as M0) abovethe MOL contacts.

Also disclosed herein are integrated circuit (IC) structures that areformed according to the disclosed methods so as to incorporate at leastone field effect transistor (FET), where the FET has a gate and where agate contact to the gate lands on a portion of the gate above (or closethereto) an active region (i.e., where a gate contact is a CBoA). Asmentioned above, the disclosed methods can be used to form IC structuresthat incorporate planar FET(s) or non-planar FET(s), that incorporate aconventional gate-first gate or a replacement metal gate, thatincorporate a complementary metal oxide semiconductor (CMOS) device withboth an N-type FET (NFET) and a P-type FET (PFET), that incorporate aCMOS device where the NFET and PFET each have multiple semiconductorbodies and have a shared gate, etc.

FIGS. 19A-19C illustrate one embodiment of such an integrated circuit(IC) structure 200 and, particularly, an embodiment of an IC structure200 that incorporates a CMOS device with both a non-planar first-typeFET 291 (e.g., an NFET) and a non-planar second-type FET 292 (e.g., aPFET), where the NFET 291 and PFET 292 share a gate 260 (e.g., areplacement metal gate) and where a gate contact 285′ to the gate 260lands, for example, on a portion of the gate 260 over an active region(i.e., where gate contact 285′ is a CBoA).

This IC structure 200 is formed, for example, on asemiconductor-on-insulator (SOI) wafer that includes a semiconductorsubstrate 202 (e.g., a silicon substrate) and an insulator layer 203(e.g., a buried oxide (BOX) layer or other suitable insulator layer onthe semiconductor substrate) and a semiconductor layer (e.g., a siliconlayer or other suitable semiconductor layer) on the insulator layer 203(as shown). Alternatively, the IC structure 200 can be formed on a bulksemiconductor wafer (e.g., a bulk silicon wafer or other suitable bulksemiconductor wafer).

The first-type FET 291 (e.g., an NFET) includes at least one firstsemiconductor body 210. The second-type FET 292 (e.g., a PFET) includesat least one second semiconductor body 220. The first and secondsemiconductor bodies 210, 220 can be formed in the semiconductor layerof an SOI wafer (or, if applicable, in upper portion of a bulksemiconductor wafer separated from the lower portion by a buried wellregion). In any case, the first and second semiconductor bodies 210, 220can, for example, be fin-shaped semiconductor bodies (i.e., relativelythin rectangular semiconductor bodies). Each first semiconductor body210 can include first source/drain regions 212 and a first channelregion 211 positioned laterally between the first source/drain regions212. Each second semiconductor body 220 can include second source/drainregions 222 and a second channel region 221 positioned laterally betweenthe second source/drain regions 222 (as discussed above and illustratedwith regard to the method steps).

A gate 260 (e.g., a gate-first gate or a replacement metal gate, asdiscussed in detail above with regard to the methods) having adielectric cap 252 and a dielectric sidewall spacer 241 can be adjacentto the semiconductor bodies 210, 220 at the respective channel regions211, 221. In the case of a non-planar FETs with a shared gate, asillustrated, the gate 260 can be adjacent to the opposing sidewalls andtop surface of each first semiconductor body 210 at the first channelregion 211 and adjacent to the opposing sidewalls and top surface ofeach second semiconductor body 220 at the second channel region 221.

Optionally, epitaxial semiconductor material can be adjacent to theopposing sidewalls and top surface of each first semiconductor body 210at the first source/drain regions 212, thereby creating a raised firstsource/drain region 213, and adjacent to the opposing sidewalls and topsurface of each second semiconductor body 220 at the second source/drainregions 222, thereby forming a raised second source/drain region 223.Optionally, the epitaxial semiconductor material on adjacent firstsource/drain regions 212 can be merged into a single region and,similarly, the epitaxial semiconductor material on adjacent secondsource/drain regions 222 can be merged into a single region, asillustrated).

In the above described FETs 291, 292, the first channel region 211 forthe first-type FET 291 (e.g., an NFET) in each first semiconductor body210 can have, for example, a second-type conductivity at a relativelylow conductivity level (e.g., a P− conductivity). The second channelregion 221 for the second-type FET 292 (e.g., a PFET) in each secondsemiconductor body 220 can have, for example, a first-type conductivityat a relatively low conductivity level (e.g., an N− conductivity).Additionally, the first source/drain regions 212 (or, if applicable, theraised first source/drain regions 213) for the first-type FET 291 can,for example, be doped with a first dopant so as to have the first-typeconductivity at a relatively high conductivity level (e.g., N+conductivity). The second source/drain regions 222 (or, if applicable,the raised second source/drain regions 223) of the second-type FET 292can, for example, be doped with a second dopant so as to have thesecond-type conductivity at a relatively high conductivity level (e.g.,P+ conductivity).

The IC structure 200 can further have at least one dielectric layer,including a conformal dielectric layer 242 and an additional dielectriclayer 250, stacked above the first source/drain regions 212 (or, raisedfirst source/drain regions 213, as illustrated) and the secondsource/drain regions 222 (or, raised second source/drain regions 223)and further positioned laterally adjacent to the dielectric sidewallspacer 241. Metal plugs 256 with additional dielectric caps 257,respectively, can be within metal plug openings that extend verticallythrough the at least one dielectric layer (e.g., through the additionaldielectric layer 250 and the conformal dielectric layer 242) to thefirst source/drain regions 212 (or, raised first source/drain regions213, as illustrated) and to second source/drain regions 222 (or, raisedsecond source/drain regions 223). Thus, the dielectric sidewall spacer241 is positioned laterally between the metal plugs 256 and the gate 260and further between the additional dielectric caps 257 and thedielectric cap 252.

The dielectric cap 252 on the gate 260, the dielectric sidewall spacer241 on the gate 260, and the additional dielectric caps 257 on the metalplugs 256 should all be made of different dielectric materials. Thesedifferent materials can be preselected so that, during subsequentprocessing (e.g., see process steps 110-114, discussed in greater detailabove), the dielectric cap 252 is selectively etchable over thedielectric sidewall spacer 241 and the additional dielectric caps 257and so that the additional dielectric caps 257 are selectively etchableover the dielectric sidewall spacer 241 and the dielectric cap 252. Theadditional dielectric layer 250 and additional dielectric caps 257 canbe made of the same dielectric material. Exemplary dielectric materialscan include, for example, silicon nitride for the dielectric cap 252,silicon carbon oxide for the dielectric sidewall spacer 241 and siliconoxide for the additional dielectric caps 257 and the additionaldielectric layer 250. Alternatively, any other suitable dielectricmaterials could be used. In any case, the dielectric cap 252 on the gate260, the dielectric sidewall spacer 241 on the gate 260, the additionaldielectric caps 257 on the metal plugs 256 and the additional dielectriclayer 250 can all have approximately co-planar top surfaces.

An interlayer dielectric material 280 can be on and, particularly,immediately adjacent to and can cover top surfaces of the dielectric cap252, the dielectric sidewall spacer 241, the conformal dielectric layer242, the additional dielectric layer 250 and the additional dielectriccaps 257. The ILD material can be, for example, silicon oxide or anyother suitable ILD material (e.g., borophosphosilicate glass (BPSG),tetraethyl orthosilicate (TEOS), fluorinated tetraethyl orthosilicate(FTEOS), etc.). After the ILD material is deposited, another CMP processcan be performed.

A first contact opening can extend vertically through the interlayerdielectric material 280 and the dielectric cap 252 to the gate 260.Additionally, second contact openings can extend vertically through theinterlayer dielectric material 280 and the additional dielectric caps257 to the metal plugs 256. The first contact opening and the secondcontact openings can be filled with conductive material to form a firstcontact to the gate 260 and second contacts to the metal plugs 256,respectively. Since the dielectric cap 252 on the gate 260 isselectively etchable over the dielectric sidewall spacer 241 and theadditional dielectric caps 257 during formation of the first contactopening, the first contact will be self-aligned to the gate 260 (i.e.,will be a self-aligned first contact), regardless of whether anymisalignment occurs during processing, and the risk of a short occurringbetween the first contact and any of the metal plugs is avoided (or atleast significantly reduced). Similarly, since the additional dielectriccaps 257 are selectively etchable over the dielectric sidewall spacer241 and the dielectric cap 252 during formation of the second contactopenings, the second contacts will be self-aligned to the metal plugs256 (i.e., will be self-aligned second contacts), regardless of whetherany misalignment occurs during processing, and the risk of a shortoccurring between any of the second contacts 286 and the gate 260 isavoided (or at least significantly reduced).

For example, referring to FIG. 19B, when the first contact opening isoffset from the gate 260 (e.g., due to overlay control issues) such thatit has a first portion that overlaps the gate 260 and a second portionthat overlaps a metal plug 256, etching of the second portion will stopon the additional dielectric cap 257 and etching of the first portionwill continue stopping on the gate 260. Thus, the first portion of themisaligned first contact opening will be deeper than the second portionand protection is provided against the development of a short betweenthe resulting misaligned first contact 285′ and the metal plug 256 uponfilling of the misaligned first contact opening with conductivematerial.

Similarly, as illustrated in FIG. 19C, when a second contact opening isoffset from a metal plug 256 (e.g., due to overlay control issues) suchthat it has a first portion that overlaps a metal plug 256 and a secondportion that overlaps the gate 260, etching of the second portion willstop on the dielectric cap 252 and dielectric sidewall spacer 241 andetching of the first portion will continue through the additionaldielectric cap 257 stopping on the metal plug 256. Thus, the firstportion of the misaligned second contact opening will be deeper than thesecond portion and protection is provided against the development of ashort between any misaligned second contact 286′ and the gate 260 uponfilling of the misaligned second contact opening with conductivematerial.

As mentioned above, the metal plugs 256 are formed within metal plugopenings that extend vertically through the additional dielectric layer250 and the conformal dielectric layer 242 below. Also, as mentionedabove, the additional dielectric layer 250 and the additional dielectriccaps 257 on the metal plugs 256 can be made of the same dielectricmaterial (e.g., silicon oxide). Thus, any portion of the additionaldielectric layer 250 that is adjacent to a metal plug 256 and that isexposed when a second contact opening is misaligned will be etched awayleaving a divot 289 (e.g., positioned laterally between the dielectricsidewall spacer 241 and the metal plug 256), as shown in FIG. 19C. Sucha divot 289 at least partially exposes a sidewall of the metal plug 256and is filled with conductive material. Thus, the interface area betweena misaligned second contact 286′ and a metal plug 256 will be increased,reducing contact resistance and improving performance.

The methods as described above are used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should be understood that the terminology used herein is for thepurpose of describing the disclosed methods and structures and is notintended to be limiting. For example, as used herein, the singular forms“a”, “an” and “the” are intended to include the plural forms as well,unless the context clearly indicates otherwise. Additionally, as usedherein, the terms “comprises” “comprising”, “includes” and/or“including” specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. Furthermore, asused herein, terms such as “right”, “left”, “vertical”, “horizontal”,“top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”,“over”, “overlying”, “parallel”, “perpendicular”, etc., are intended todescribe relative locations as they are oriented and illustrated in thedrawings (unless otherwise indicated) and terms such as “touching”,“on”, “in direct contact”, “abutting”, “directly adjacent to”, etc., areintended to indicate that at least one element physically contactsanother element (without other elements separating the describedelements). The corresponding structures, materials, acts, andequivalents of all means or step plus function elements in the claimsbelow are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Therefore, disclosed above are methods of forming an integrated circuit(IC) structure, which includes one or more field effect transistors(FETs). The disclosed methods allow for a gate contact to be formed on aportion of a gate aligned above an active region of a FET (i.e., a CBoA)or to be formed close thereto (e.g., to be formed on a portion of a gatein close proximity to the active region and/or in close proximity to anymetal plugs). The disclosed methods also provide protection against thedevelopment of shorts between the gate contact and any metal plugs onthe FET source/drain regions and further between the gate andsource/drain contacts to the metal plugs. Specifically, in the methods,a gate with a dielectric cap and dielectric sidewall spacer can beformed on the channel region of a FET or, optionally, on the channelregions of multiple FETs. Additionally, metal plugs with additionaldielectric caps can be formed on the source/drain regions of the FET orFET(s) such that the dielectric sidewall spacer is positioned laterallybetween the gate and the metal plugs and further between the dielectriccap on the gate and the additional dielectric caps on the metal plugs.The dielectric cap, dielectric sidewall spacer and additional dielectriccaps can be made of different dielectric materials preselected to beselectively etchable, thereby allowing for possible misalignment of thecontact opening to the gate without risking exposure of any metal plugsand vice versa. Also disclosed are resulting IC structures.

What is claimed is:
 1. An integrated circuit structure comprising: asemiconductor body for a field effect transistor, the semiconductor bodycomprising source/drain regions and a channel region positionedlaterally between the source/drain regions; a gate having a dielectriccap and a dielectric sidewall spacer, the gate being adjacent to thesemiconductor body at the channel region; at least one dielectric layerabove the semiconductor body at the source/drain regions and positionedlaterally adjacent to the dielectric sidewall spacer; metal plugs havingadditional dielectric caps, the metal plugs being within metal plugopenings in the at least one dielectric layer and aligned above thesource/drain regions, wherein the dielectric cap, dielectric sidewallspacer and additional dielectric caps comprise different dielectricmaterials, and wherein the dielectric sidewall spacer is positionedlaterally between the metal plugs and the gate and further between theadditional dielectric caps and the dielectric cap; interlayer dielectricmaterial above the dielectric cap, the dielectric sidewall spacer andthe additional dielectric caps; a first contact comprising conductivematerial in a first contact opening extending vertically through theinterlayer dielectric material and the dielectric cap to the gate; andsecond contacts comprising the conductive material in second contactopenings extending through the interlayer dielectric material and theadditional dielectric caps to the metal plugs.
 2. The integrated circuitstructure of claim 1, wherein the first contact opening lands on thegate adjacent to an active region of the field effect transistor.
 3. Theintegrated circuit structure of claim 1, wherein the dielectric cap, thedielectric sidewall spacer and the additional dielectric caps haveapproximately co-planar top surfaces.
 4. The integrated circuitstructure of claim 1, wherein, due to the different dielectricmaterials, the dielectric cap is selectively etchable over thedielectric sidewall spacer and the additional dielectric caps duringformation of the first contact opening to allow for misalignment of thefirst contact opening without shorting of the first contact to any ofthe metal plugs and wherein, due to the different dielectric materials,the additional dielectric caps is selectively etchable over thedielectric sidewall spacer and the dielectric cap during formation ofthe second contact openings to allow for misalignment of any of thesecond contact openings without shorting of any of the second contactsto the gate.
 5. The integrated circuit structure of claim 1, wherein thedifferent dielectric materials comprise silicon nitride for thedielectric cap, silicon carbon oxide for the dielectric sidewall spacerand silicon oxide for the additional dielectric caps.
 6. The integratedcircuit structure of claim 1, wherein the gate comprises a replacementmetal gate.
 7. The integrated circuit structure of claim 1, furthercomprising a dielectric layer above the source/drain regions, thedielectric layer having plug openings containing the metal plugs andfurther having a divot that is adjacent to a metal plug sidewall andthat is filled with the conductive material.
 8. An integrated circuitstructure comprising: a semiconductor body for a field effecttransistor, the semiconductor body comprising source/drain regions and achannel region positioned laterally between the source/drain regions; agate having a dielectric cap and a dielectric sidewall spacer, the gatebeing adjacent to the semiconductor body at the channel region; at leastone dielectric layer above the semiconductor body at the source/drainregions and positioned laterally adjacent to the dielectric sidewallspacer; metal plugs having additional dielectric caps, the metal plugsbeing within metal plug openings in the at least one dielectric layerand aligned above the source/drain regions, wherein the dielectric cap,dielectric sidewall spacer and additional dielectric caps comprisedifferent dielectric materials, and wherein the dielectric sidewallspacer is positioned laterally between the metal plugs and the gate andfurther between the additional dielectric caps and the dielectric cap;interlayer dielectric material above the dielectric cap, the dielectricsidewall spacer and the additional dielectric caps; a first contactcomprising conductive material in a first contact opening extendingvertically through the interlayer dielectric material and the dielectriccap to the gate, wherein the first contact opening further extendslaterally over the dielectric sidewall spacer and further over anadditional dielectric cap such that the first contact is above andimmediately adjacent to top surfaces of the dielectric sidewall spacerand the additional dielectric cap; and second contacts comprising theconductive material in second contact openings extending through theinterlayer dielectric material and the additional dielectric caps to themetal plugs.
 9. The integrated circuit structure of claim 8, wherein thefirst contact opening lands on the gate adjacent to an active region ofthe field effect transistor.
 10. The integrated circuit structure ofclaim 8, wherein the dielectric cap, the dielectric sidewall spacer andthe additional dielectric caps have approximately co-planar topsurfaces.
 11. The integrated circuit structure of claim 8, wherein, dueto the different dielectric materials, the dielectric cap is selectivelyetchable over the dielectric sidewall spacer and the additionaldielectric caps during formation of the first contact opening to allowfor misalignment of the first contact opening without shorting of thefirst contact to any of the metal plugs and wherein, due to thedifferent dielectric materials, the additional dielectric caps isselectively etchable over the dielectric sidewall spacer and thedielectric cap during formation of the second contact openings to allowfor misalignment of any of the second contact openings without shortingof any of the second contacts to the gate.
 12. The integrated circuitstructure of claim 8, wherein the different dielectric materialscomprise silicon nitride for the dielectric cap, silicon carbon oxidefor the dielectric sidewall spacer and silicon oxide for the additionaldielectric caps.
 13. The integrated circuit structure of claim 8,wherein the gate comprises a replacement metal gate.
 14. The integratedcircuit structure of claim 8, further comprising a dielectric layerabove the source/drain regions, the dielectric layer having plugopenings containing the metal plugs and further having a divot that isadjacent to a metal plug sidewall and that is filled with the conductivematerial.
 15. An integrated circuit structure comprising: asemiconductor body for a field effect transistor, the semiconductor bodycomprising source/drain regions and a channel region positionedlaterally between the source/drain regions; a gate having a dielectriccap and a dielectric sidewall spacer, the gate being adjacent to thesemiconductor body at the channel region; at least one dielectric layerabove the semiconductor body at the source/drain regions and positionedlaterally adjacent to the dielectric sidewall spacer; metal plugs havingadditional dielectric caps, the metal plugs being within metal plugopenings in the at least one dielectric layer and aligned above thesource/drain regions, wherein the dielectric cap, dielectric sidewallspacer and additional dielectric caps comprise different dielectricmaterials, and wherein the dielectric sidewall spacer is positionedlaterally between the metal plugs and the gate and further between theadditional dielectric caps and the dielectric cap; interlayer dielectricmaterial above the dielectric cap, the dielectric sidewall spacer andthe additional dielectric caps; a first contact comprising conductivematerial in a first contact opening extending vertically through theinterlayer dielectric material and the dielectric cap to the gate,wherein the first contact opening further extends laterally over thedielectric sidewall spacer and further over an additional dielectric capsuch that the first contact is above and immediately adjacent to topsurfaces of the dielectric sidewall spacer and the additional dielectriccap; and second contacts comprising the conductive material in secondcontact openings extending through the interlayer dielectric materialand the additional dielectric caps to the metal plugs, wherein at leastone of the second contact contact openings extends laterally over thedielectric sidewall spacer and the dielectric cap such that at least oneof the second contacts is above and immediately adjacent to top surfacesof the dielectric sidewall spacer and the dielectric cap.
 16. Theintegrated circuit structure of claim 15, wherein the first contactopening lands on the gate adjacent to an active region of the fieldeffect transistor.
 17. The integrated circuit structure of claim 15,wherein the dielectric cap, the dielectric sidewall spacer and theadditional dielectric caps have approximately co-planar top surfaces.18. The integrated circuit structure of claim 15, wherein, due to thedifferent dielectric materials, the dielectric cap is selectivelyetchable over the dielectric sidewall spacer and the additionaldielectric caps during formation of the first contact opening to allowfor misalignment of the first contact opening without shorting of thefirst contact to any of the metal plugs and wherein, due to thedifferent dielectric materials, the additional dielectric caps isselectively etchable over the dielectric sidewall spacer and thedielectric cap during formation of the second contact openings to allowfor misalignment of any of the second contact openings without shortingof any of the second contacts to the gate.
 19. The integrated circuitstructure of claim 15, wherein the different dielectric materialscomprise silicon nitride for the dielectric cap, silicon carbon oxidefor the dielectric sidewall spacer and silicon oxide for the additionaldielectric caps.
 20. The integrated circuit structure of claim 15,further comprising a dielectric layer above the source/drain regions,the dielectric layer having plug openings containing the metal plugs andfurther having a divot that is adjacent to a metal plug sidewall andthat is filled with the conductive material.